Computational Nanotechnology, DETEMA, Facultad de Química, UDELAR, CC 1157, 11800 Montevideo, Uruguay.
Chemistry. 2011 Feb 7;17(6):1979-87. doi: 10.1002/chem.201002840. Epub 2011 Jan 12.
By means of first principle calculations we have investigated a set of molecules that are presumed to contain carbon-sulfur triple bonds, namely HCSOH, H(3)SCH, cis-FCSF, F(3)CCSF(3), and F(5)SCSF(3). For HCSOH, FCSF, and H(3)SCH we used the CCSD(T) methodology and the correlation-consistent basis sets. On the other hand, F(3)CCSF(3) and F(5)SCSF(3) were studied at the B3LYP, M06-2X, MP2, and G3 levels of theory. We found that none of these molecules display a carbon-sulfur adiabatic bond dissociation energy (ABDE) as strong as diatomic CS (170.5 kcal mol(-1)), or a diabatic bond dissociation energy (DBDE) larger than the one found in SCO (212.0 kcal mol(-1)), although the DBDE of FCSF comes quite close at 208.3 kcal mol(-1). The CS ABDEs of F(3)CCSF(3), F(5)SCSF(3), and H(3)SCH are comparable to that of a single C-S bond. In contrast with the experimental results, F(3)CCSF(3) and F(5)SCSF(3) are predicted to be linear with C(3v) and C(s) symmetry, respectively, at the B3LYP/6-311+G(3df,2p) level. MP2/6-311+G(2df,2p) calculations support the C(3v) symmetry for F(3)CCSF(3), despite F(5)SCSF(3) not having a perfect linear structure; the CSC angle is 174.6°, which is nearly 20° larger than the experimental value. The analysis of the carbene structures of HCSOH and H(3)SCH revealed that they are not significant, because the triplet state is dissociative in these cases. However, for F(3)CCSF(3) and F(5)SCSF(3) , the carbene triplet states lie 0.81 and 0.77 eV above the singlet state, respectively. In the same vein, our investigation supports the presence of a strong double bond for HCSOH. The conflicting evidence available for F(3)CCSF(3) and F(5)SCSF(3) makes it very difficult to determine the nature of the CS bonds. However, the bond dissociation energies and the singlet-triplet splittings clearly suggest that these compounds should be considered as masked sulfinylcarbenes. The analysis of the bond dissociation energies challenges the existence of a triple bond in these five molecules, but from a strictly thermodynamic standpoint, cis-FCSF is found to be the candidate most likely to exhibit triple-bond character.
通过第一性原理计算，我们研究了一组假定含有碳-硫三键的分子，即 HCSOH、H(3)SCH、cis-FCSF、F(3)CCSF(3)和 F(5)SCSF(3)。对于 HCSOH、FCSF 和 H(3)SCH，我们使用了 CCSD(T)方法和相关一致的基组。另一方面，F(3)CCSF(3)和 F(5)SCSF(3)则在 B3LYP、M06-2X、MP2 和 G3 理论水平上进行了研究。我们发现，这些分子中没有一个具有像双原子 CS(170.5 kcal mol(-1))那样强的碳-硫绝热键离解能(ABDE)，或者像 SCO(212.0 kcal mol(-1))那样大的离解能(DBDE)，尽管 FCSF 的 DBDE 相当接近 208.3 kcal mol(-1)。F(3)CCSF(3)、F(5)SCSF(3)和 H(3)SCH 的 CS ABDE 与单个 C-S 键相当。与实验结果相反，F(3)CCSF(3)和 F(5)SCSF(3)在 B3LYP/6-311+G(3df,2p)水平下分别预测为具有 C(3v)和 C(s)对称性的线性分子。尽管 F(5)SCSF(3)没有完美的线性结构，但 MP2/6-311+G(2df,2p)计算支持 F(3)CCSF(3)的 C(3v)对称性；CSC 角为 174.6°，比实验值大近 20°。对 HCSOH 和 H(3)SCH 卡宾结构的分析表明，它们并不重要，因为在这些情况下三重态是离解的。然而，对于 F(3)CCSF(3)和 F(5)SCSF(3)，卡宾三重态分别比单重态高出 0.81 和 0.77 eV。同样，我们的研究支持 HCSOH 存在强双键。对于 F(3)CCSF(3)和 F(5)SCSF(3)，现有的相互矛盾的证据使得确定 CS 键的性质变得非常困难。然而，键离解能和单重态-三重态分裂清楚地表明，这些化合物应该被视为掩蔽的亚磺酰基卡宾。键离解能的分析对这五种分子中存在三键提出了质疑，但从严格的热力学角度来看，cis-FCSF 被认为是最有可能表现出三键特征的候选物。
